EX-32.1 4 tmb-20250630xex32d1.htm EX-32.1

Exhibit 32.1

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CERTIFICATION PURSUANT TO

18 U.S.C. SECTION 1350,

AS ADOPTED PURSUANT TO

SECTION 906 OF THE SARBANES-OXLEY ACT OF 2002

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In connection with the Quarterly Report of Old Second Bancorp, Inc. (the “Company”) on Form 10-Q, as filed with the Securities and Exchange Commission on the date hereof (the “Report”), I, James L. Eccher, Chief Executive Officer of the Company, certify, pursuant to 18 U.S.C. § 1350, as adopted pursuant to § 906 of the Sarbanes-Oxley Act of 2002, that:

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(1) The Report fully complies with the requirements of Section 13(a) or 15(d) of the Securities Exchange Act of 1934; and

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(2) The information contained in the Report fairly presents, in all material respects, the financial condition and result of operations of the Company.

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Ay 13 | ​ | ​
August 7, 2025 | /s/ James L. Eccher | ​
​ | James L. Eccher
​ | Chairman and Chief Executive Officer (principal executive officer)
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